Subjective wavefront refraction using continuously adjustable wave plates of zernike function

ABSTRACT

A wavefront device produces adjustable amplitudes in optical path differences and adjustable axis orientation angles. two substantially identical wave plates have a wavefront profile of at least the third order Zernike polynomial function which are not circularly symmetric, as denoted by Z(i,j) where i≧3 and j≠0. The wave plates are mounted in rotatable mounts with their optical centers substantially aligned with each other. An subjective wavefront refraction instrument and method are provided to correct low and high order aberrations of the eye, using the adjustable wave plates that have astigmatism and higher order Zernike function optical path difference wavefront profiles.

PRIORITY

This application is a Divisional of U.S. patent application Ser. No.11/746,051, filed May 8, 2007, now U.S. Pat. No. 7,726,811; claims thebenefit of priority to U.S. provisional patent application No.60/746,772, filed May 8, 2006, and is a Continuation in Part (CIP) ofU.S. patent application Ser. No. 11/675,079, filed Feb. 14, 2007, nowU.S. Pat. No. 7,699,471; which claims priority to U.S. provisionalpatent application No. 60/773,758, filed Feb. 14, 2006.

BACKGROUND

Before the advent of the wavefront aberrometer, many patients' visualsymptoms were collectively referred to as a result of “irregularastigmatism”. Increasingly, more ophthalmologists and optometrists havebegun measuring wavefront errors of patients' eye. A wealth ofinformation is now available, that was not heretofore, fromauto-refractor or cornea topography measurements. Use of a wavefront mapas a diagnosis tool is also gaining popularity, and vision careprofessionals use it to explain diagnoses to patients having visualcomplaints.

It is useful to understand the source of a problem. However, patientsare most interested in solutions; such as getting rid of visualcomplaints, and improving their quality of vision. Currently, laserrefractive surgery, such as LASIK, is one possible solution. However,laser surgery is invasive and the tissue healing process followingsurgery can induce its own set of aberrations, often rendering anattempt to correct the pre-operation errors fruitless. It has beenproposed to correct high order aberrations (HOA) with non-invasivedevices such as spectacles or contact lenses.

It was proposed in US application 2004/0160576A1, which is herebyincorporated by reference, to identify high order wavefront errors witha patient feedback control process.

However, lacking in that disclosure is the basis for a patient to adjusteach of the wavefront components. The '160576 application does discloseuse of visual acuity as a measure to find an end point. As it waspointed out in the '160576 application, an acuity chart, or Snellenletter chart, is not an ideal target for wavefront optimization. Moreimportantly, no method is presented regarding how a patient may choosewhich Zernike function to vary among the dozens of Zernike functions,without which the patient would have to go on a random walk, using bytrial and error on all or substantially all of the Zernike functions.Without a clear step by step procedure, a patient may not even be ableto find an optimal sphere, cylinder and axis, much less the high orderZernike components, wherein the effect of those aberrations on acuity ismuch smaller. The patient might get totally lost in the process, and itmight take hours to come to any final optimized combination, if it evergot there at all.

RECOGNIZED BY THE INVENTOR

Improving quality of vision is more complicated than measuring the HOAand canceling them. Higher order aberrations are typically much smallerin amplitude compared to the defocus and astigmatism terms, and theyvary from eye to eye. The question arises as to whether there would bevisual benefits by correcting them in some patients. Also, the brainplays a key part in interpreting and in forming perceived images of whatone sees. The optical image formed at the retina is only a startingpoint.

If one can measure the HOA; then one can cancel them optically. However,as it was pointed out, it is not clear whether if this cancellationresults in improvement in one patient, then the same approach will workfor a different patient.

In embodiments described herein, tools are provided for performing asubjective method for a patient. In a preferred embodiment, not just thesphere and cylinder and axis are handled, but the HOA errors arerefracted as well. That is, using a technique in accordance with apreferred embodiment, a patient can actually see through a combinationof wave plates that are adjustable in amplitude, and preferably also inangle.

With this technique, a patient can actually see whether a wavefrontcorrection, as presented to the patient, provides any benefits. Asubjective technique in accordance with a preferred embodiment stands incontrast with objective techniques in which HOA errors of an eye aremeasured and a spectacle or contact lens is provided to cancel the HOA,and wherein the patient finds out only later if the device offers anybenefits at all when he or she receives the corrective device.

In a preferred embodiment, an instrument is provided that comprises waveplates of Zernike functions, each of which is continuously adjustable inamplitude, and preferably also in angle. In addition, a continuouslyvariable wave plate assembly is alternatively provided for utilizing aseries of wave plates in small increment steps. These wave plates can bearranged on a disk, like a series of lenses in a phoropter, and thesystem can be made affordable for most eye care professionals.

SUMMARY OF THE INVENTION

A wavefront device that produces adjustable amplitudes in optical pathdifferences and adjustable axis orientation angles is provided. Twosubstantially identical wave plates have a wavefront profile of at leastthe third order Zernike polynomial functions which are not circularlysymmetric, as denoted by Z(i,j) where i≧3 and j≠0. The wave plates aremounted in rotatable mounts with their optical centers substantiallyaligned with each other.

The device may include a pinion gear engaging with bevel gears includingat least one bevel gear attached to each of the rotatable mounts,wherein rotating the pinion gear may cause the wave plates to rotate inopposite direction at a substantially equal angular rate to cause achange in amplitude of the device. Electric motors with drive mechanismsmay drive the wave plates at a same angular rate substantially insynchronization, while the wave plates move in equal amount and inopposite direction to change a wavefront amplitude. The wave plates aremoved in a same direction to change an optic axis angle direction.

A method of generating a subjective optical prescription with a Zernikewave plate having an ability to substantially continuously adjust itsamplitude and optic axis angle is also provided. Two substantiallyidentical wave plates have a wavefront profile of a Zernike polynomialfunction. Optical centers of the wave plates are aligned. The waveplates are rotated in opposite direction in one or more substantiallyidentical angular amounts until a patient indicates an optimal setting.The entire assembly is rotated including the two wave plates to an opticaxis angle indicated as optimal by the patient. An optical prescriptionis generated based on initial positions and rotation amounts of the twowave plates. The rotating of the two wave plates may include rotating apinion gear which engages with bevel gears that are mounted with thewave plates.

A method of determining second order and higher order aberrations of apatient's eye is also provided. Zernike functions are provided in apredetermined order in a priority list. At least one point source isprovided as a viewing target. A first adjustable wave plate is selectedaccording to the order in the priority list. The first adjustable waveplate is placed in a patient's line of sight. A refractive error of thepatient is minimized by adjusting amplitude and angle of the firstadjustable wave plate while the patient is looking at the viewingtarget. These are repeated for one or more further wave plates accordingto the order in the priority list, until no appreciable furtherimprovement in image quality of the point source is observed by thepatient.

The priority list may include Z(2,0), Z(2,+/−2), and Z(3,+/−1), in thatorder, and may further include Z(3+/−3) after Z(3,+/−1), and may furtherinclude Z(4,+/−2), Z(5,+/−1), Z(4,+/−4), Z(5,+/−3), Z(6,+/−2),Z(6,+/−4), Z(5,+/−5), in that order, after Z(3+/−3). The placing of thefirst adjustable wave plate may include positioning the first wave plateof the Zernike function at a conjugate corneal or pupil plane of thepatient.

Refractive errors of third or higher order Zernike function aberrationsmay also be minimized. An input device is provided to the patient. Anoptic axis angle of an adjustable wave plate of third or higher orderZernike profile which is disposed at a conjugate corneal or pupil planeof the patient is varied while the patient is looking at the viewingtarget. An amplitude of the adjustable wave plate of third or higherorder is varied also while the patient is looking at the viewing target.An indication is received from a patient that a predetermined end pointhas been reached by activation of the input device, The method may alsoinclude varying the angle of the wave plate of third or higher order,finding an optimal angle position, and then varying the amplitude of theadjustable wave plate. The predetermined end point may include asharpest image of the point source target as indicated by the patient.

Contact or intraocular lenses may be provided and/or an ablation profileof refractive surgery may be determined such as for LASIK, PRK, LASEK,and/or intra-corneal surgery.

A method of correcting refractive errors of second and higher orderaberrations of an eye is also provided. Second order aberrations aredetermined using adjustable Z(2,0) and Z(2,+/2) Zernike wave plates.Higher orders aberrations are corrected using Z(2,0) and higher Zerniketerms, wherein Z(2,0) substantially corrects aberrations of all higherorder Zernike terms that are spherically symmetric.

A further device for determining or correcting aberrations of an eye isalso provided. The device includes at least one adjustable wave platehaving adjustable amplitude and optic axis angle. A priority list ofZernike functions is provided such that adjustable wave plates may beselected in accordance with an order of Zernike functions in the list. Apoint source is provided as a viewing target. The one or more selectedwave plates are placed at a conjugate corneal or spectacle plane of apatient's eye. A patient searches for predetermined image end pointswhile looking at the point source while angle and amplitude of theselected wave plate are varied.

The priority list may include Z(2,0), Z(2,+/−2), and Z(3,+/−1), in thatorder, and may further include Z(3+/−3) after Z(3,+/−1), and may furtherinclude Z(4,+/−2), Z(5,+/−1), Z(4,+/−4), Z(5,+/−3), Z(6,+/−2),Z(6,+/−4), Z(5,+/−5), in that order, after Z(3+/−3). The placing of thefirst adjustable wave plate may include positioning the first wave plateof the Zernike function at a conjugate corneal or pupil plane of thepatient.

The ordering of the priority list may be modified according to anaberration amplitude of the patient's eye in Zernike function asdetermined by a subjective wavefront aberrometer. The priority list maybe modified by a condition of the patient's eye, including a keratoconusand/or a corneal transplant condition. The priority list may be modifiedby weighting factors with relative values affecting the ordering of thelist as determined by the clinical experience of a physician.

The adjustable wave plate may include adjustable wave plates Z(2,0) andZ(2,+/−2), and/or another wavefront device such as liquid crystal waveplates or deformable mirrors. The other wavefront device may produceadjustable amplitudes in optical path differences and adjustable axisorientation angles, and include two substantially identical wave plateswith wavefront profile of at least the third order Zernike polynomialfunction, which are not circularly symmetric, as denoted by Z(i,j) wherei≧3 and j≠0. The wave plates may be mounted in rotatable mounts withtheir optical centers substantially aligned with each other.

The adjustable wave plate may include at least one substantiallyidentical pair of wave plates having a Zernike function optical pathdifference profile, a deformable mirror and/or a liquid crystal waveplate.

An optical instrument is also provided for generating a prescription forone or more corrective lenses or corrective procedures for a patient bysubjective refraction. The instrument includes a stable frame having adefocus corrector assembly (DCA) and an astigmatism corrector assemblycoupled thereto. The DCA causing a change of defocus power at thepatient's eye, and includes a first motor and at least two DCA lensesdisposed along an optical axis between an image source and the patient'seye. At least one of the DCA lenses is movable relative to the framealong the optical axis for adjusting defocus power and/or is replaceablewith one or more further lenses with incremental dioptric powers. Thedefocus power may be thereby measurably adjustable until the patientindicates that an initially blurry view of the image source has becomesubstantially sharp. The ACA causes a change of astigmatism power, andincludes a second motor and at least two astigmatism plates disposedalong the optical axis that are relatively rotationally adjustableand/or wherein at least one of the ACA astigmatism plates is replaceablewith one or more further cylindrical lenses. The astigmatism power isthereby measurably adjustable until the patient indicates that aninitially elongate view of the image source has become substantiallyround.

The instrument may further include electrical and/or electronicshardware and/or computer programs for performing individually orcollectively one or more of the following tasks:

-   -   (i) drive movement of one or more optical elements in the DCA or        ACA, or both, to change defocus or astigmatism power, or both;    -   (ii) display a location of an optical element;    -   (iii) convert a location or orientation reading, or both, to a        refractive power in units of diopters;    -   (iv) collect data relating to adjustments to the DCA and ACA;    -   (v) set limits of movement range for the DCA or ACA or both to        avoid over-correction;    -   (vi) automatically advance DCA or ACA refractive power, or both,        when such task is requested; or    -   (vii) automatic align the ACA optical axis when such task is        requested, or combinations thereof.

The ACA may provide a variable astigmatism correction amplitude orvariable axis angle, or both. The ACA may include a first wave platehaving a second order Zernike polynomial of astigmatism wavefrontcorrection profile in an x-y plane. A second wave plate may have asecond order Zernike polynomial of astigmatism wavefront correctionprofile in the x-y plane. The first and the second wave plates may bemounted with their wavefront profile origins aligned along an axis(Z-axis). One or more of the wave plates may be angularly adjustablewith respect to said Z-axis. The wavefront profile of the Zernikepolynomial of astigmatism of the first and second wave plates mayinclude Z(2,2) or Z(2,−2). Both of the wave plates may be angularlyadjustable with respect to the Z-axis.

First and second ACA astigmatism plates may be mounted on first andsecond rotary ball bearings, and first and second bevel gears may becoupled to the first and second ball bearings. A first pinion gear maydrive the first and second bevel gears for oppositely rotating the firstand second ACA plates. A second motor may drive the first pinion gear. Arotary angle sensing device may be coupled to a rotary encoder. A secondpinion gear may be mounted between the first and second bevel gears.

The ACA may be further for causing a change in orientation of axisangle. At least two astigmatism plates of said ACA may be rotatabletogether as a whole. The optical instrument may further include thirdand fourth ball bearings coupled to the first and second ball bearings,respectively, and to the frame. A third bevel gear may be coupled to atleast one of the third and fourth ball bearings. A third motor may befor rotating the astigmatism plates of the ACA assembly together. Asecond rotary encoder may be coupled to a fourth pinion gear for sensingangular rotation of the ACA assembly.

The instrument may include an optics holder for each of the DCA lenses.A linear slide may be coupled to the optics holder of at least one ofthe DCA lenses. A motor and lead screw may move the linear slide.

A computer program product may include a processor and a computerprogram for calculating amplitudes of the ACA plates from relativeand/or absolute angular movement and/or for calculating diopter power ofthe DCA. Readable results may be output. The computer program productmay also form an ordered list of decreasing significance of Zernikefunctions based on RMS amplitude of a patient's measured wavefronterrors. The computer program product may also control measurementsaccording to the ordered list. Measurements for Zernike functions havinga RMS amplitude less than 0.05 may be omitted. The ordered list mayinclude second order Zernike function, Coma, Trefoil and secondaryastigmatism.

The optical instrument may further include an input device for thepatient or for an examination administrator or both. The image sourcemay include a plane wave light source including substantially a pointlight source as a viewing target. A quality vision marker (QVM) mayinclude one or more display items including one or more lines, one ormore circles, one or more points disposed along a pattern of one or morelines or circles, or combinations thereof. The marker may provide adisplay pattern including one or more rings and/or parallel lines. Areference marker may provide a sweep line overlapping at the imagesource and having an orientation which is adjustable using the at leastone input device until the patient indicates that the sweep line isaligned with a sharper linear image of the image source. Axis angle dataof astigmatism errors of the patient's eye may be thereby provided.

The image source may include a plane wave point source placed two metersor farther away from the patient and having a diameter of twomillimeters or less, or a substantially collimated light beam from alaser source that simulates a point source positioned two meters orfarther away from the patient. An additional lens may be disposed tocause the image source to appear to the patient to be two meters orfarther away. Spectral contents of the image source may include whitelight, substantially blue light, substantially yellow light, orsubstantially red light.

One or more spectacle, contact or intraocular lenses may have aprescription based on measurements by the optical instrument describedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates subjective refraction apparatus in accordance withan embodiment.

FIG. 1B illustrates a quality vision marker (QVM) including point lightsource in accordance with an embodiment.

FIG. 2 schematically illustrates an optical instrument in accordancewith an embodiment.

FIG. 3 is a flow chart illustrating a subjective refraction method inaccordance with an embodiment.

FIG. 4 is a flow chart illustrating a fine tuning of a subjectiverefraction method in accordance with an embodiment.

FIG. 5 is a flow chart illustrating correction of high order aberrationsin accordance with an embodiment.

FIG. 6 illustrates a subjective refraction apparatus in accordance withanother embodiment.

DETAILED DESCRIPTION OF PREFERRED AND ALTERNATIVE EMBODIMENTS

In the entire specification, the term “wavefront refraction” shall bebroadly construed to include any process of providing wavefrontcompensation to a patient's eye, while the patient is looking at atarget. A “wavefront refractor” is a device which an eye careprofessional may use to perform refraction that includes correctinghigher order aberrations of the eye, or sometimes referred to as higherorder refractive errors. The “+/−” is also used herein before the secondindex of Zernike functions to represent a grouping of the pair ofZernike polynomials that have a same first index, wherein the secondindex has opposite sign. For example, the pair of Trefoil, Z(3,−3) andZ(3,3) are to be paired, and Z(3,+/−3) shall designate a combination ofthe two Trefoils in an adjustable wave plate configuration. The termwave plate shall mean an optical plate that has the property of inducingan optical path difference profile. When a light wave passes the plate,the spatial profile across the two dimensions of the plate surface has achange in its wavefront in accordance with the optical path differenceprofile. A Zernike wave plate shall mean the optical path difference hasa cross sectional profile as that of a Zernike function profile. Theoptical axis of a Zernike function may be assigned in accordance with amajor symmetry axis of the Zernike function. For example the opticalaxis of Z(2,+/−2) can be chosen either at zero degree or 90 degrees, andin this case selected according to an assignment of cylindrical cylinderlens axis.

Construction of Continuously Adjustable Zernike Function Wave Plates

The Zernike function wave plates described in the following can bemanufactured using high precision free form diamond turning CNC machine,which is commercially available from Schneider, Germany. We adapt theOptical Society of America (OSA) convention for the Zernike functions,but omit the normalization constant for convenience. Using the trefoilsas an example, and adding an amplitude and angular notation in theZernike function designation. Two Zernike functions of Trefoil bothhaving an amplitude of unity, and at an angle θ, are expressed as:Z(3,−3,1,θ)=ρ³ sin(3θ)Z(3,+3,1,θ)=ρ³ cos(3θ)

Note that: Z(3,−3, 1,θ)=Z(3,+3, 1,θ+90/3), namely, the two trefoils inthe Zernike polynomial functions are in fact identical except for anangular offset of 30 degrees.

Suppose that one desires to have a variable wave plate of trefoil withvariable amplitude ranging from 0 to 5. One first fabricates twoidentical Trefoil wave plates each with an amplitude of 2.5:Z(3,−3,2.5,θ)=2.5 ρ^(sin) (3θ).

One achieves a total cancellation if one rotates one trefoil in the pairby 30 degrees relative to the second trefoil.Z((3,−3,2.5,0+30)=2.5 ρ³ sin (3(θ+30))=−2.5 ρ³ sin (3θ)Z(3,−3,2.5,θ)+Z(3,−3,2.5,θ+30)=Z(3,−3,2.5,θ)−Z(3,+3,2.5,θ)=0

When two identical Trefoils are aligned:Z(3,−3,2.5,θ)+Z(3,−3,2.5,θ)=Z(3,−3,5,θ).

Now, one can vary the Trefoil pair to any amplitude value, between 0 and5, by rotating one or the other. It is preferable to rotate the pairsimultaneously in identical angle, or approximately, but in oppositedirection. That way, the optical axis of the combined wave plateassembly remains stationary, while the amplitude is adjusted.

The sum amplitude of 5 from a pair of plates with amplitude of 2.5 isused merely as an example for illustration. No limitation is to beinferred on the range of the amplitude of the Zernike wave plateassembly using a technique in accordance with a preferred embodiment.

Likewise, one can construct continuously adjustable Coma wave plates bysubstantially following the above steps, except replacing the Zernikefunction designation from a Trefoil to a Coma designation, basically byreplacing the second index +/−3, inside the bracket, with +/−1.

For the fourth order Zernike terms, like tetrafoils Z(4,+/−4, 1,θ), themethod described above also applies. In this case, the continuouslyadjustable device comprises two tetrafoil wave plates of equalamplitude. However, the total cancellation, or the zero tetrafoil,occurs when the relative angle θ is at 90/4, or 22.5 degrees. Moreover,the technique of this preferred embodiment may also be used to constructcontinuously adjustable secondary-tetrafoils Z(4,+/−2, 1,θ), because theangular part of the secondary-tetrafoil is identical to the those oftetrafoils.

Zernike functions other than those with a zero in the second index, suchas Z(4,0), Z(6,0), etc., can be paired off (those terms that have almostidentical designation, except for a plus/minus sign difference in thesecond index in their functional representation), and a continuouslyadjustable device can be constructed using the technique provided above.

The Visual Significance of Symmetric Zernike Functions and theirCorrection

Concerning the Zernike terms of fourth order and higher, and having asecond index of zero, the following three points are noted. First, theseterms are symmetric in nature, while irregularly shaped corneas thatcause serious visual symptoms and complaints such as keratoconus areseldom rotationally symmetric. Second, the point spread functionresulting from these aberration terms have a tight focus, but with somehalo effect at nighttime around bright light sources. The visual acuityis not so affected during daytime, but the contrast sensitivity wouldsuffer to some extent. Third, and fortunately, the defocus term Z(2,0)can be used effectively to counteract these aberrations, canceling most,if not all, of the aberration from these fourth order and higher Zerniketerms. Therefore, the compromise on the quality of vision may be madesmall and even negligible by not having a continuously adjustablesymmetric wave plate for Z(4,0), Z(6,0) and those of even higher orderterms.

Subjective Wavefront Refractor Having Continuously Adjustable ZernikeFunction Wave Plates

Previously, the same inventor has filed patent applications entitled,“Subjective wavefront refraction correcting low and high orderaberrations”, corresponding to U.S. application Ser. Nos. 60/773,758 and11/675,079, which are incorporated by reference in their entirety.

In these referenced applications, a subjective refraction device isdescribed, which comprises two continuously adjustable assemblies, onefor the defocus Z(2,0), and one for astigmatism Z(2,+/−2). Using thedevice and method according to the referenced applications, the secondorder terms correct a good portion of the high order aberrations.However, there will be residual HOA.

High Order Zernike Wave Plates in a Wavefront Refractor

Instead of positioning the Zernike wave plates right next to thepatient's eye, which would be crowded, the wave plates may beadvantageously positioned in accordance with another embodiment at theequivalent pupil plane (refer to FIG. 1, element 225 is a plane wherethe wave plates are located) after the Defocus Corrector Assembly 200,or DCA 200 in FIG. 1. FIG. 1(a) of U.S. application Ser. No. 60/773,758is incorporated into the present specification as FIG. 1 forillustration. A wave plate can be any of a variety of optical devicesthat have a distribution of optical path differences across theirtransverse extent relative to the optical path within which they arepositioned. A lens and a curved mirror are examples. A lens may berotationally symmetric, but in the case of a trefoil, e.g., it is not. Awave plate is any reflective or transmissive optic corresponding to aselected Zernike function. For example, another wave plate is a comawave plate. A wave plate assembly in accordance with a preferredembodiment includes at least two wave plates that can be relativelydisplaced to change optical amplitude or angle or both.

FIG. 1 schematically illustrates the optical layout of a device inaccordance with a preferred embodiment. A conjugate pupil plane 225 ofthe patient's eye under examination is located at approximately thefocal point 225 of the lens f2, 220 in FIG. 1, between the lens f2 220and the target 110. The target is located ideally for positioning apupil limiting aperture or pinhole as discussed in the referencedapplication. Preferably, the wave plate assembly that is located atplane 225 is also mounted on a same movable platform as the lens f2(220) is mounted on. Thereby, the distance between lens f2 (220) and thewave plate assembly that is located at plane 225 remains the same whenlens f2 (220) is moved to provide an adjustable defocus diopter power.

Process which Utilize the Wavefront Reactor Overcoming the PatientSelection Problem of Objective Wavefront Refraction Methods

One drawback of the objective method of refracting a patient is the lackof patient feedback. Until now, commercial wavefront aberrators havebeen limited to measuring optical aberrations of the eye. Some haveattempted to correct aberration by canceling it by way of incorporatingan exact opposite of the wavefront error profile in spectacles orcontact lenses. Ideally, if all the optics are aligned properly, theresulting image that forms at the retina of the patient would bediffraction limited. One remaining issue is that the patient may notappreciate the difference of the high order wavefront corrected imagecompared to that corrected with the second order, namely, sphere,cylinder and axis.

Therefore in accordance with certain embodiments, a measured total orderwavefront error is input into the wavefront refractor. Communicatingwith the wavefront refractor is a computer running a computer programcoupled to control the drive mechanism. The computer is preferably usedto control the movement of the optical components including the defocuscorrector assembly 200 including lens f1 (210) and lens f2 (220), theastigmatism assembly 300 including optics 310 and 320 shown at thespectacle plane 400 in FIG. 1, and the high order Zernike function waveplates located at plane 225 in FIG. 1, setting them to cancel thepatient's wavefront error. Now, the patient looks through correctionoptics, including the low order optics 200, 300, and the high order waveplates at location 225, and looks at a viewing target such as a nearlycollimated light beam, a small point source, real physical objects, ahigh definition image from a monitor, or an image from film, or acombination thereof. The patient can then decide if the high ordercorrection does make a difference, and make a decision on the purchaseof just regular eyeglasses or contact lenses, or instead pay a premiumfor a wavefront corrected device in accordance with a preferredembodiment. A device in accordance with a preferred embodimenteliminates uncertainty involved in “patient selection”. Without thesubject patient participation, objective wavefront refraction inherentlyinvolves a prior patient selection algorithm. Since no algorithm canreliably read a patient's mind, such would quite likely select the wrongcandidate from time to time, with negative consequences involvingpatient complaints and demands for a refund of the purchase amount.

Subjective Wavefront Refraction with Patient Participation

In another embodiment, a patient subjectively adjusts wave plates, e.g.,located at plane 225 in FIG. 1, to achieve optimized vision. One may usea device in accordance with a preferred embodiment to generate an HOAwavefront by selecting a combination of the Zernike function waveplates, in selected amplitudes and angles. In addition, the wave platesmay comprise substantially all Zernike functions, while the patient'svision is being tested. Also, the patient can now subjectively determinean improvement in vision quality by adding/subtracting a Zernikefunction wave plate, and/or changing the amplitude and the angle of aZernike function.

Forming an Ordered List of Decreasing Significance of Zernike Functions

It is recognized by the present inventor that there is greatsignificance in establishing a procedure that leads to a finalrefraction point.

In one embodiment, a list is established for Zernike functions in anorder of decreasing significance, and uses this ordered list to guidethe patient to find the end point of subjective wavefront refraction.Here, the Zernike functions are paired with the same first index, andthe second index has the numeral except in opposite sign. Trefoils maybe used as an example. It was shown above that the two trefoils are infact identical in profile except for a relative rotation of 30 degrees.Henceforth, +/− notation is used in the second index of a Zernikefunction to denote pairing of two Trefoil functions.Z(3,+/−3,a,ψ)=Z(3,−3,b,θ)+Z(3,+3,c,θ),where “a” represents the resulting amplitude after combining the twotrefoils with amplitude “b” and “c”, and the angle ψ is the angle oforientation of the optical axis of the resulting trefoil.

In one embodiment, defocus Z(2,0) is given the top position in theordered list, followed by astigmatism (amplitude and angle). In thefollowing, an exemplary ordered list of Zernike functions is provided inthe OSA designation, and/or a modified OSA designation with the Zernikepairing schemes as proposed in an earlier paragraph:

-   -   1. Z(2,0)    -   2. Z(2,+/−2)    -   3. Z(3,+/−1)    -   4. Z(3,+/−3)    -   5. Z(4,+/−2)    -   6. Z(5,+/−1)    -   7. Z(4,+/−4)    -   8. Z(5,+/−3)    -   9. Z(6,+/−2)    -   10. Z(6,+/−4)    -   11. Z(5,+/−5)    -   12. . . .

The amplitude distribution of Zernike functions in normal human eyesdrops rapidly after the fourth order terms (OSA), and second order termsare ordinarily the most prominent. The ordered list above may continuewith more terms. However, the contribution of the remaining terms isexpected to be small, except in cases of keratoconus eyes and thoseafter corneal transplant surgery or traumatization, or the like. Theexact ordering of the Zernike components in the list is not a limitationto the invention or embodiments thereof. In another embodiment, theplacement of terms of the Zernike function in the ordered list ismodified according to clinical experience learned from patient feedbackwhen the method is used in clinical practice over time. Thereafter, amodified ordered list is to be established, or customized for aparticular situation with the patient, whether the eye has keratoconusconditions or post corneal transplant.

In another embodiment, if a patient's wavefront error has been measuredwith a subjective wavefront aberrometer, it would be clear that certainZernike terms are more dominant and some Zernike terms such as coma ortrefoil are small or missing altogether. The small Zernike terms, withRMS amplitude of less than 0.03 microns can be skipped over from theordered list, during the subjective wavefront refraction process. Inanother embodiment, the Zernike function is ordered in accordance withthe RMS amplitude of the patient's wavefront errors, and the mostdominant Zernike term gets moved up the list, and is followed by thenext highest amplitude term, and so on.

Subjective Wavefront Refraction Procedure

In the previous U.S. application Ser. Nos. 60/773,758 and 11/675,079,detailed procedures have been given to achieve optimized values for loworder Zernike terms, Z(2,0) and Z(2,+/−2), traditionally called thedefocus and astigmatism and axis angle. In the optimization process, therefractive errors relating to defocus and astigmatism is substantiallyreduced. One advantageous aspect of this refraction method is in eachelement of the process, there is a distinct end point for the patient tosearch for. Therefore, each element may be achieved without confusion.What follows are exemplary end points for arriving at optimalprescriptions for eyeglasses, or contact lenses. The prescription mayalso be used for refractive surgery. Distinct end points may include:

-   -   1. Without correction, a patient would typically see a diffuse        image of a point source viewing target. First, defocus        refractive error is substantially removed by continuously adding        or subtracting refractive power using the DCA device, until a        relative sharp line image, or an otherwise elongated image, is        formed from the point source target.    -   2. To correct for the astigmatism, the ACA device is adjusted to        turn the line, or elongated image, and/or condense it into a        substantially round image.    -   3. Next, the defocus power is increased or decreased, depending        on whether the refraction is for a positive or negative cylinder        convention, and the round image is condensed into substantially        a point image.    -   4. For correction of a higher order aberration, greater than the        second order Zernike aberrations, one attempt to reduce star        bursts around a point image may be achieved in (3) above. The        defocus and astigmatism may be further adjusted. Moreover,        adjustments may be added with other higher order wave plates        such as coma and trefoil. Third and higher order Zernike        function wave plates may be used to further tighten the point        image into a sharp point substantially free of star bursts.

In certain embodiments, one Zernike wave plate assembly is tested at atime. A point source, or multiple point sources as described in Ser.Nos. 60/773,758 and 11/675,079, may be presented to the patient as theviewing target. As in the previous disclosure, the points, orsubstantially the points may be arranged in a certain predeterminedpattern to facilitate and improve test speed and accuracy. In testing awave plate of third order or higher in Zernike function, the end pointto be searched by a patient undergoing an eye examination is to achievea sharpest focused point image of the point or points at the viewingtarget.

In accordance with an embodiment, after the low order Zernike terms havebeen determined, one selects the next Zernike function term from anordered list. The list illustrated above under the heading, “Forming anOrdered List of Decreasing Significance of Zernike Functions”, or amodified, abridged or expanded list, can then be used as a default list.Some re-arrangement may be derived from evidenced success from clinicalfeedbacks, as discussed. Assuming that clinical data confirms thesignificance ordering of Zernike functions in the list above, then as anexample, and without inferring any limitation, the next most significantZernike function can then be selected, which in this example isZ(3,+/−1), known as the “Coma”. One may first increase the amplitude asan example, in 0.05 micron increments, and between each incrementalstep, the patient may rotate the coma assembly axis angle to find thebest angular position. Again, a substantially collimated light source ispreferably used as our viewing target for the high order wavefrontrefraction procedure. Alternatively, a small point source positionedsufficiently far away from the patient can also be used. The importanceand the usefulness of using such a target has been discussed in the U.S.application Ser. Nos. 60/773,758 and 11/675,079 which have already beenincorporated by reference. It offers sufficient sensitivity for findinga final refraction end point. The end point for the patient to searchfor is the tightest point image with least amount of star bursts. Thestar bursts are related and indicative of the existence of higher orderaberrations of the vision of the patient.

Some steps of adjusting, back and forth between the amplitude and theangle change are expected. Preferably, the patient has one hand on oneknob controlling the amplitude, and the other hand on a knob adjustingthe angle. The process can move along quickly, such that these stepswill not lead the patient to a state of confusion.

Once the end point for Coma is reached, the wave plate assembly is keyedup for the next Zernike function to be adjusted in a similar manner asis done for the Coma wave plate assembly. Once the end point of thatZernike function is reached, one moves on to the wave plate assembly ofthe next most significance Zernike function to present to the patientalong his/her line of sight at the location as specified, and so forth.

If there is no perceived improvement in the quality of the image when itreaches a certain Zernike on the significance list, at say term number7, Z(5,+/−1), Secondary Coma, as it is sometimes referred to, in ourexample shown in the last section, then the wavefront refractionprocedure is preferably considered completed.

Even though the feature of being able to continuously vary the amplitudeof the wave plate is a significant advantage, we place no limitation onapplying all mentioned methods and test techniques to perform a visionimprovement test with a series of wave plates having discrete incrementsin wave amplitude, in place of the continuous variable wave plate deviceas presented here. Such discrete plates may be mounted on a wheel, e.g.,like those in a phoropter, and/or on translational stages to be moved inand out of the line of sight of the patient under test.

Detailed Mechanism for Continuous Adjustability in Wave Plate Assembly

In accordance with another embodiment, a motorized mechanism is providedfor a Zernike function wave plate assembly, which is applicable to anyof the Zernike functions included in this specification. In a preferredembodiment, as illustrated at FIG. 2, a pair of Zernike wave plates aremounted on a rotary ball bearing. One of the wave plate pairs is shown,labeled 720, on bearing 710. Only one of the pair is shown. A view ofthe second ball bearing and of the second wave plate is blocked in FIG.2, while the mounting and the motion mechanism is similar to that of thefirst wave plate. The inner ring of the ball bearing 710 is attached toa bevel gear 740. Similarly, the second wave plate is mounted with asecond ball bearing, and the inner portion of the second ball bearing isattached to a second bevel gear 742.

In one embodiment, two pinion gears are used. One pinion gear 760 may beused to drive both bevel gears, as illustrated in FIG. 2, which in turnrotate the pair of wave plates in equal angles but in oppositedirection. This counter rotating motion of the Zernike wave plate pairaccomplishes the goal of adjusting the amplitude value of the combinedwave plate assembly. As it is stated above, and in U.S. applicationsSer. Nos. 60/773,758 and 11/675,079, when two identical wave plates of aselected Zernike function are substantially aligned with overlappingoptical axes, the paired wave plates generate the maximum wavefrontamplitude. Using again the Trefoil example, if one uses two wave plates,each with amplitude of 2.5, the maximum amplitude achievable is the sum,or 5. As the relative angle between the wave plate pair increases, theoverall amplitude of the assembly unit decreases, and the sum amplitudebecomes zero when the optical axis of the two Trefoils are at 90/3, or30 degrees apart. Therefore, an amplitude control ranges from zero to amaximum of 5. Other desirable adjustable ranges may be constructedsimilarly utilizing two identical wave plates each having half of adesired maximum.

A motor unit 770 illustrated in FIG. 2 is attached to a drive piniongear 760. The motor unit 770 can include a DC motor, a step motor, oranother suitable mechanism that turns the pinion gear 760. A secondpinion gear 750 is also preferably mounted between the two bevel gears740 and 742. This second pinion gear is used as a rotary angle sensingdevice and is attached to a rotary encoder 780. Electrical output is fedto an encoder reader which reads pulses and pulse edges. Thisinformation is converted to an angular position of the optical axis ofeach of the wave plates. A second computer program routine thencalculates the sum amplitudes of the two wave plates, from the relativeangular movement for a given amplitude of the individual wave plates. Anoverall amplitude of the wave plate pair is then displayed in a monitor,LED, LCD, or any suitable display device, including thermal printer.

Outer rings of ball bearings 730 and a corresponding outer ring for thesecond ball bearing are attached to inner rings of third and fourth ballbearings. The outer rings of the third and the fourth ball bearings arein turn supported and mounted to the base of the instrument (not shown).The outer ring of the fourth bearing 790 is shown in FIG. 2, but theview of its inner ring is obscured. That inner ring of the fourth ballbearing 790 is attached to a third bevel gear 800. The entire counterrotating unit of the first and second bearings are affixed to the innerring of the fourth bearing 790, and a second motor 870 is connected toand drives the third pinion gear 860, which in turn rotates the entirecounter rotating assembly comprising the first and second ball bearingsand the counter rotating wave plates. A second rotary encoder 820 isattached to a fourth pinion gear 810 and senses an angular rotation ofthe entire counter rotating assembly, which is the angle ψ, of theoptical axis of the entire counter rotating wave plate pair. Again, theelectrical output of the encoder 820 is fed to an encoder reader. Aseparate computer routine converts electrical pulses from the encoderinto an angle reading, which is the angular orientation ψ, of theoptical axis of the wave plate pair.

Alternate Method of Driving the Continuous Variation in Amplitude andAngle

Instead of using pinion gears to drive the two wave plates of the ACA,which are preferably substantially identical, in opposite direction,preferably at identical angular rates or otherwise in identical angularamounts per increment, one may use synchronized motor drives. In suchconstruction, each wave plate is driven by its own driver electronics.However, two driver circuits are controlled by a closed loop algorithm,such that the two motors still move substantially in “lock-step”, ormove continuously or jog in steps, in substantially identical angleincrements in the same or opposite directions, during any commandedmovement. The motor movement is monitored by rotatory encoder. Anamplitude precision greater than 0.01 diopters is in this way achievablein a 6 diopter astigmatism adjustable wave plate unit.

A Mechanical Design for a Wavefront Refractor

In the previous paragraph, an embodiment was described of a continuouslyadjustable wave front generation unit of a Zernike function of secondorder or higher, with non-zero second index (except Z(2,0). Thestructure of this may be as described in the U.S. application Ser. Nos.60/773,758 and 11/675,079. Zernike function wave plates are not madewith a symmetric generating machine with two axis grinding andpolishing, such as those used to generate sphere and cylindricalsurfaces in spectacle lenses. A high precision commercial 4-axis and5-axis freeform generator machine can cut a surface profile and evenpolish along the contoured surface. One expects each of such custom-madewave plates would be much more costly. This is an advantage of thetechnique of certain embodiments which use only two wave plates tocreate infinite and variable amplitudes and angles, as compared to otherembodiments that use a series of wave plates at fixed amplitude, andincremental amplitudes, similar to a series of lenses on a disk inside aphoropter. The former technique also overcomes the problem of requiringa large number of wave plates each with smaller increments in amplitude.

Indeed, FIG. 2 also represents an embodiment of a structural design ofthe optical layout of a wavefront refractor as described in U.S.application Ser. Nos. 60/773,758 and 11/675,079. That instrument couldbe manufactured with only two continuously adjustable Zernike functions,i.e., the astigmatism and the defocus. The astigmatism wave plateassembly (300 of FIG. 1) is shown on the left in FIG. 2, and is alsoreferred to as an illustration of how other continuously adjustable waveplate assemblies may be constructed. The defocus assembly (200 inFIG. 1) includes two lenses f1 (210 of FIGS. 1) and f2 (220 of FIG. 1),which are mounted in optics holders 910 and 920, respectively. The lensmount 920 is affixed on a linear slide 930, which is movable along theoptical axis of the patient's line of sight. A linear encoder strip 940is attached to the movable platform 932, and an encoder reader head 942,generates electrical pulses as the encoder strip travels across it. Theencoder output is fed to a pulse counter, and a computer routine is usedto covert the count into the location of lens f2 relative to f1, and itsubsequently calculates the diopter power of the defocus assembly unit.The diopter reading is displayed preferably by a suitable method such aswas mentioned in the case of the rotary encoder.

The movable platform of the linear slide is driven by a lead screw 950,which is turned by a motor 960. Any kind of motor with the desiredspeed, resolution and accuracy may be used.

FIGS. 3-5 illustrate steps or operations or functions that may beperformed in accordance with methods of preferred and alternativeembodiments. FIG. 3 illustrates elements 510-594, FIG. 4 illustrateselements 610-674 and FIG. 5 illustrates elements 710-770. These may beperformed in different orders and one or more may be skipped inalternative embodiments. These are also non-exhaustive examples, andadditional steps, operations or functions may be added or replaced intothe technique. Descriptions of these processes are provided in detail inthe parent U.S. application Ser. No. 11/675,079, which is incorporatedby reference.

Using Alterative Devices to Generate Adjustable Wavefront Profile

While devices and methods have been described in detail for performingsubjective wavefront refraction using continuously adjustable waveplates of Zernike functions, the present invention is not limited to aparticular type of continuously adjustable wave plates, such as thepreferred embodiment that has been described above, namely, anadjustable assembly including two Zernike wave plates of identical, orapproximately identical, first index, except that the second index is ofopposite sign, Z(i,+/−j), where i and j are the first and the secondindices respectively, of the Zernike function. In other embodiments, thecontinuously adjustable Zernike wavefront profile may be replaced byother wavefront profile generating devices and methods, such as adeformable mirror, a liquid crystal phase plate, or another suitabledevice that is capable of generating adjustable Zernike wave amplitudeand angle. Alternative devices can be much more costly and complicatedto operate for a clinical instrument.

The appropriate selected device is preferably placed at a conjugateplane of the patient's pupil or spectacle plane. In the case of using aliquid crystal wave plate, it is placed at the location of thepreviously described wave plate assembly. In one embodiment, during therefraction process for an optimal wavefront correction, again using theexample above and assuming the ordered list is the optimal list, afterthe second order Zernike function wave plates have been optimized forthe patient, the next Zernike function to be optimized is Coma. Againthe patient is given two knobs for adjustment control, one to adjust theamplitude and one for the angle. The liquid crystal wave plate generatesa Coma in accordance with the input from the control knobs, while thepatient is looking at the target, which may be a nearly collimated lightsource, or other appropriate variation of the target.

So far this alternative process is substantially the same as describedpreviously. Next, moving down the ordered Zernike list, the next step isto optimize the Trefoil. When a Trefoil wavefront profile is requestedvia signals generated from the patient's turning of knobs, the wavefrontprofile of the liquid crystal is to be changed to be the sum profile ofthe Coma amplitude and angle as arrived at from the last optimizationfor the Coma function. A computer or an appropriate microprocessor is toreceive the input from the patient (the knobs in this case, but this isnot a limiting factor), and computer routine will preferably perform thesum calculation of (1) the previously arrived at Coma wavefront(amplitude and angle) and (2) the requested Trefoil amplitude and angle.The resulting profile of the sum (Coma and Trefoil) is then sent to theliquid crystal wave plate controller, which generates electricalsignals, each of which is to be directed to a specific location of theliquid crystal wave plate, and a two dimensional wavefront profile isthen generated. When different signs are received from the knobs, a newTrefoil amplitude or angle is requested. This new Trefoil replaces thelast Trefoil, and a new sum wavefront profile (old Coma and new Trefoil)is generated from the computer and is sent to the liquid crystalcontroller, and so forth, until optimal Trefoil is reached.

The process is then repeated for the next Zernike function down theordered list. In this example, Z(4,+/−2), or the secondary astigmatism,is to be optimized for the same patient. When that is optimized, thenext Zernike function in the ordered list is to be optimized, and soforth, until no improvement is perceived or perceivable by the patientand the optimization process is considered completed.

Alternative Method of Searching for Optimal End Point for BothAdjustable Wave Plates and Alternative Variable Wavefront ProfileGenerating Devices such as Liquid Crystal Phase Plate or DeformableMirrors

In another embodiment, a quick and automated method is provided. Insteadof providing the test subject with two knobs to control the angle andthe amplitude independently, a computer program is used in this case toscan the angle of the wave plate continuously, at a given amplitudevalue of the Zernike wave plate. For example, an optimized trefoil is tobe determined in a test. First, the amplitude of trefoil is set, e.g.,at 0.2 microns, and the angle of the optic axis is scanned by thecomputer quickly. The test subject then presses an input device such asa mouse or a knob, or joystick, or executable display, orvoice-activation, to indicate that he or she has seen an improvementpoint. Repeated scans may be used to check the reliability of the testsubject's input for repeatability at or near the same angle ororientation of the wave plate. In one embodiment, if no appreciableimprovement is indicated, or an improvement is indicated, the computerincreases the amplitude and scans the angle as before. In thisembodiment, the test is continued until the test subject presses asecond input device indicating the target image quality has become worserather than improved. Values of the amplitude and the angle at the bestvision are noted, e.g., stored in a permanent or removable memory deviceor printed out on a report, display, or pdf.

Alternatively, if the test subject has confirmed the angle locationaccurately more than once, the angle orientation of the wave plate maybe set at that orientation, and the computer then changes the amplitude,i.e. to increase, or decrease, again in a scanning fashion. The computermonitors the test subject's input to indicate image quality improvementor deterioration. This method substantially increases the test speed,and arrives at the end point of the sharpest image of the target moreefficiently.

Referring now to FIG. 6, a deformable mirror 230 or curved reflectingoptic 230 may be used, instead of a transmissive assembly such as aliquid crystal wave plate that was indicated as being located at plane225 in FIG. 1. The wavefront is reflected from the mirror 230, ratherthan passing through a wave plate or an adjustable Zernike wave plateassembly located at plane 225 in FIG. 1. Reflective optics such asmirrors are to be added in the path of the line of sight of the patientto re-direct the traveling wave from the target to the patient. In FIG.6, the front surface of a deformable mirror 230 is positioned at theconjugate focal plane of the patient's pupil, similar to the previouslydescribed technique. A difference is that a reflective surface of mirror230 is nearly facing the lens f2, 220 of FIG. 6, or at least rayspassing through lens f2 220 encounter reflective optic 230 along theoptical path towards target 110. Mirror 230 is also tilted slightly toallow rays traveling along the light path to encounter a plane mirror240 which is offset from the optical path between lens f2 220 and mirror230. This offset prevents blocking by mirror 240 of the view between thelens f2 220 and the deformable mirror 230. The plane mirror 240 is alsooriented along a path towards the target light source 110. A wavefrontrefraction technique uses a deformable mirror 230 that preferably servesa substantially same function as using a liquid crystal wave plate 225(see FIG. 1), except electric signals are sent to actuators that deformthe mirror surface to generate the requested shape to generate theoptical path difference.

Beneficial Applications

Once an optimized vision of a test subject has been arrived at, awavefront correction for that person's eye is determined subjectively bythe test subject. A correction wavefront profile may be used in a numberof vision correction devices or surgery methods. When wavefrontcorrection is used in eyeglasses, contact lenses, or intraocular lenses,the profile correction is typically incorporated by a construction ofmaterial thickness profile in such devices. When the wavefrontrefraction is used in surgical correction methods including PRK, LASIK,LASEK, and intra-corneal surgery, the wavefront correction is achievedby designing a tissue ablation profile either on the cornea or under thecorneal flap, or inside the stroma via the use of a femtosecond laser asan example.

The present invention is not limited to the embodiments described aboveherein, which may be amended or modified without departing from thescope of the present invention as set forth in the appended claims, andstructural and functional equivalents thereof.

In methods that may be performed according to preferred embodimentsherein and that may have been described above and/or claimed below, theoperations have been described in selected typographical sequences.However, the sequences have been selected and so ordered fortypographical convenience and are not intended to imply any particularorder for performing the operations.

In addition, the subject matter disclosed in all references cited aboveherein, in addition to the background and summary of the inventionsections and including U.S. Pat. Nos. 5,984,916, 6,210,401, 6,325,792,6,706,036, 6,761,454, 7,114,808, and 7,188,950, are hereby incorporatedby reference into the detailed description of the preferred embodimentsas disclosing alternative embodiments and components.

I claim:
 1. An optical instrument for generating a prescription for oneor more corrective lenses or corrective procedures for a patient bysubjective refraction, comprising: (a) a stable frame; (b) at least onepoint source as a viewing target disposed outside the patient's eye; (c)a defocus corrector assembly (DCA) coupled to the frame for causing achange of defocus power at the patient's eye, the DCA including at leasttwo DCA lenses disposed along an optical axis between the at least onepoint source as said viewing target and a position configured forplacement of a patient's eye to permit the patient to view the target;and (d) an astigmatism corrector assembly (ACA) coupled to the frame forcausing a change of astigmatism power including at least two Zernikeastigmatism waveplates disposed along the optical axis, wherein said ACAfor causing a change in orientation of axis angle, and wherein said atleast two Zernike astigmatism waveplates of said ACA are rotatabletogether as a whole and not configured as cylindrical lens elements. 2.The optical instrument of claim 1, including at least two DCA lensesdisposed along an optical axis between an image source and a patient'seye, and further including a first motor.
 3. The optical instrument ofclaim 2, and further including second motor coupled with a system of oneor more gears for relatively rotating the astigmatism plates formeasurably adjusting astigmatism power until the patient indicates asecond condition with regard to the patient's view of the image source.4. The optical instrument of claim 3, and further including a thirdmotor coupled with a system of one or more gears for synchronouslyrotating the astigmatism plates for measurably adjusting astigmatismaxis angle until the patient indicates a third condition with regard tothe patient's view of the image source.
 5. The optical instrument of anyof claim 1, 2, 3 or 4, further comprising electrical or electronicshardware or computer programs, or combinations thereof, for performingindividually or collectively one or more of the following tasks: (i)display a location of an optical element; (ii) convert a location ororientation reading, or both, to a refractive power in units ofdiopters; (iii) collect data relating to adjustments to the DCA and ACA;or (iv) set limits of movement range for the DCA or ACA or both to avoidover-correction; or (v) combinations of (i), (ii), (iii) and (iv). 6.The optical instrument of claim 1, further comprising automaticallyadvancing DCA or ACA refractive power, or both, when such task isrequested; or automatic aligning the ACA optical axis when such task isrequested, or combinations thereof.
 7. The optical instrument of claim1, further comprising a first rotary ball bearing upon which a first ACAastigmatism plate is mounted.
 8. The optical instrument of claim 7,further comprising a first bevel gear coupled to the first ball bearing.9. The optical instrument of claim 8, further comprising a second ballbearing upon which a second ACA astigmatism plate is mounted.
 10. Theoptical instrument of claim 9, further comprising a second bevel gearcoupled to the second ball bearing.
 11. The optical instrument of claim10, further comprising a first pinion gear for driving the first andsecond bevel gears for oppositely rotating the first and second ACAplates.
 12. The optical instrument of claim 11, wherein said secondmotor for driving said first pinion gear.
 13. The optical instrument ofany of claim 1, 2, 3 or 4, further comprising a rotary angle sensingdevice coupled to a rotary encoder.
 14. The optical instrument of claim4, wherein said ACA for causing a change in orientation of axis angle,and wherein said at least two astigmatism plates of said ACA arerotatable together as a whole.
 15. The optical instrument of claim 9,wherein said optical instrument further comprises third and fourth ballbearings coupled to the first and second ball bearings, respectively,and to the frame.
 16. The optical instrument of claim 15, furthercomprising a third bevel gear coupled to at least one of the third andfourth ball bearings, and also comprising a third motor, for rotatingthe at least two astigmatism plates of the ACA assembly together. 17.The optical instrument of claim 16, further comprising a second rotaryencoder coupled to a fourth pinion gear for sensing angular rotation ofthe ACA assembly.
 18. The optical instrument of claim 1, furthercomprising an optics holder for each of the DCA lenses.
 19. The opticalinstrument of claim 18, wherein the linear slide is coupled to theoptics holder of at least one of the DCA lenses.
 20. The opticalinstrument of claim 19, further comprising a lead screw coupled with thefirst motor and linear slide for moving the at least one DCA lens. 21.The optical instrument of claim 1, further comprising a computer programproduct including a processor and a computer program for calculatingamplitudes of the ACA plates from relative or absolute angular movementor for calculating diopter power of the DCA, or combinations thereof,and outputting readable results.
 22. The optical instrument of claim 21,wherein said computer program product further for forming an orderedlist of decreasing significance of Zernike functions based on RMSamplitude of a patient's measured wavefront errors.
 23. The opticalinstrument of claim 22, wherein said computer program product furtherfor controlling measurements according to the ordered list.
 24. Theoptical instrument of claim 23, wherein measurements for Zernikefunctions having a RMS amplitude less than 0.05 are omitted.
 25. Theoptical instrument of claim 22, wherein the ordered list includes secondorder Zernike function, Coma, Trefoil and secondary astigmatism.
 26. Theoptical instrument of claim 1, wherein the first condition comprises aninitially blurry view of the image source becoming a substantially sharppoint or elongated.
 27. The optical instrument of claim 26, wherein thesecond condition comprises an initially elongate view of the imagesource becoming substantially round or a focused point image.
 28. Theoptical instrument of claim 1, wherein the second condition comprises aninitially elongate view of the image source becoming substantiallyround.